This document discusses tuning a PID controller for a pH system. An open loop step change was used to determine system parameters. Direct synthesis was then used to derive controller coefficients that reached the set point in 120 seconds. Controller coefficients were doubled to compare performance, with direct synthesis performing best. In summary, direct synthesis is a favorable tuning method for controlling pH.

1. TUNING A PH PID
CONTROLLER
Julia Fletcher
Renee Chuang
Anthony Yeoman
Jiayue Yu
University of California, San Diego
Jacobs School of Engineering

2. A batch system, with a strong acid and
base was under investigation.
Transmits Signal
(http://ucsd-ceng-176.wikia.com)

3. The PBS solution was titrated to identify
the buffer region.
0
2
4
6
8
10
12
0 50 100 150 200
pH
Time(s)
Titration Curve
Buffer Region = 6.5 - 7.8 pH

4. An open loop step change was used to
determine Kp & 𝜏 of the system.
KKp: .000954
𝜏: 24.17

5. The Direct synthesis method was used to
derive equations for controller coefficients.
System
Model
Controller Coefficients

6. The coefficients found via direct synthesis was
observed to reach set point at 120 seconds.
7.2
7.3
7.4
7.5
7.6
7.7
7.8
7.9
8
8.1
0 20 40 60 80 100 120 140 160
pH
Time(s)
𝐾𝑐 = 6.074
𝜏 𝐷= 24.17

7. Controller coefficients were doubled and
compared to each other.
7.2
7.4
7.6
7.8
8
8.2
8.4
0 20 40 60 80 100 120 140
pH
Time(s)
Double Kc
Double tau_deri
Direct Synthesis
Set point

8. In summary, direct synthesis is a favorable tuning
method when trying to control pH.
(www.setis-systems.com)

9. In summary, direct synthesis is a favorable tuning
method when trying to control pH.
Questions?(www.setis-systems.com)